Adverse reaction to neuromuscular blockers: frequency, investigation, and epidemiology.

A survey is presented of neuromuscular drug involvement in 390 clinically severe anaphylactoid reactions (grades II-IV reported to a Sheffield laboratory from 1988 to the end of 1992 from hospitals throughout the UK. Despite advances in patient monitoring and newer drugs, the reporting frequency and individual drug involvement were remarkably similar to those of a previous report from the laboratory in 1988. The highly immunogenic drug suxamethonium still predominated (48% of reports), but there was now much reduced use of the similarly immunogenic drug, alcuronium. The incidence of reactions to vecuronium and atracurium remained similar (12% and 18% reports, respectively) and acceptable to the anaesthetist. However, in choosing drugs for individual patients, the anaesthetist may wish to note that vecuronium reactors mainly showed bronchospasm, and atracurium reactors hypotension. By a systematic laboratory investigation, based on measurement of plasma tryptase and urinary methylhistamine, reaction mechanisms were assessed in 53 reactions. Despite their overall clinical similarity, analysis revealed that only one reaction in three was likely to be due to IgE-mediated anaphylaxis (Type 1). Not only was suxamethonium the most frequently reported drug, but in this study 11 reactions were identified as Type 1 response: no allergic reactions were identified for either vecuronium or atracurium, although single cases were identified for alcuronium, gallamine, and tubocurarine, with two unidentified. The remaining reactions were judged to be non-immune, although most involved mast cell degranulation. These reactions were no less hazardous than Type 1 reactions (one death), and two deaths were recorded. The importance of laboratory investigation as a feature of postreaction care is emphasized.